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<div class="moz-cite-prefix">Thanks for your reply!<br>
<br>
Ah. Sigh.<br>
<br>
Its on Ubuntu 14.04 LTS. The "critical need" is for backups and
failover. I know I can use LVM, but we have had more problems with
LVM that we have had with bare disks (and tar backups); especially
when it came to disk failures.<br>
<br>
On 08/21/2015 04:23 PM, Alan Johnson wrote:<br>
</div>
<blockquote
cite="mid:CAAhwQiiih6rMWwrNxN+kAyOxY7R187faaH13nhEVWwhtW9k1xw@mail.gmail.com"
type="cite">
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<div class="gmail_default"
style="font-family:verdana,sans-serif">The host is some linux
or other? Running with that assumption, I don't expect you
will get anything extra out of zfs if you are only using it
for pooling vs. LVM. As long as you are handing a block
device to the guest, the IO overhead of the virtualization is
pretty much nil. Now, if you were using regular files to back
your virtual drives instead of block devices, ZFS (not just
zpool) on the host might get you something, but I depends on a
lot of things, and I would never advocate putting a file
system on a file system if you care at all about IO. That's
where your IO overhead comes in. Passing it to a KVM/libvirt
guest does not introduce anything of concern on modern
hardware (maybe an extra processor instruction or 2 here and
there).</div>
<div class="gmail_default"
style="font-family:verdana,sans-serif"><br>
</div>
<div class="gmail_default"
style="font-family:verdana,sans-serif">If you don't already
know and love ZFS with all its beauty and risks, and you don't
have a specific critical need for it, I recommend against it.
ext4 on LVM does a great job for 99.99% of use cases and the
support and user community for it is second to none. I found
this not to be the case with FreeNAS/BSD/ZFS when I had a year
long nightmare with it some time ago on what is admittedly now
likely and aged version of ZFS.</div>
<div class="gmail_default"
style="font-family:verdana,sans-serif"><br>
</div>
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<div class="gmail_extra"><br>
<div class="gmail_quote">On Fri, Aug 21, 2015 at 3:33 PM, Bruce
Dawson <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:jbd@codemeta.com" target="_blank">jbd@codemeta.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> For this rainy
weekend, please consider the following:<br>
<br>
I'm constructing a new server and want 2 KVM guest systems
on it. There are 3 4TB drives on it. At the moment, assume
one 4TB drive will be reserved for the KVM host. The
server has 16GB of RAM.<br>
<br>
What are the advantages/disadvantages of:<br>
<ol>
<li>Putting all disks in a ZFS pool on the host and
dividing the pool between each guest. Or:</li>
<li>Giving each guest its own disk. (At least one of the
guests will be running ZFS).</li>
</ol>
<p>The guests will be:<br>
</p>
<p> * Both guests will be running DNS servers<br>
* One guest will be running a Postfix/Dovecot mail
server (including mailman)<br>
* The other guest will be running a LAMP stack.<br>
</p>
<p>Hints: <br>
* I don't particularly like option 2 as I'll lose the
benefits of ZFS (snapshot backups, striping, ...)<br>
* I don't know if the performance benefits of ZFS
will outweigh the overhead of KVM/libvirt.<span
class="HOEnZb"><font color="#888888"><br>
</font></span></p>
<span class="HOEnZb"><font color="#888888">
<p>--Bruce<br>
</p>
</font></span></div>
<br>
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<br>
</blockquote>
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<br>
<br clear="all">
<div><br>
</div>
-- <br>
<div class="gmail_signature">
<div dir="ltr">
<div>
<div dir="ltr">
<div><span style="font-family:verdana,sans-serif">Alan
Johnson</span><br>
</div>
<div><font face="verdana, sans-serif"><a
moz-do-not-send="true"
href="mailto:alan@datdec.com" target="_blank">alan@datdec.com</a></font>
<div><span
style="font-size:16px;font-variant:small-caps;text-align:center;background-color:rgb(255,255,255)"><a
moz-do-not-send="true"
href="http://xkcd.com/1179/" target="_blank"><font
face="verdana, sans-serif">Date Format PSA</font></a></span></div>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
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